Plasmodium chabaudi chabaudi malaria parasites can develop stable resistance to atovaquone with a mutation in the cytochrome b gene

<p>Abstract</p> <p>Background</p> <p><it>Plasmodium falciparum</it>, has developed resistance to many of the drugs in use. The recommended treatment policy is now to use drug combinations. The atovaquone-proguanil (AP) drug combination, is one of the treatment and prophylaxis options. Atovaquone (ATQ) exerts its action by inhibiting plasmodial mitochondria electron transport at the level of the cytochrome bc1 complex. <it>Plasmodium falciparum in vitro </it>resistance to ATQ has been associated with specific point mutations in the region spanning codons 271-284 of the <it>cytochrome b </it>gene. ATQ -resistant <it>Plasmodium yoelii </it>and <it>Plasmodium berghei </it>lines have been obtained and resistant lines have amino acid mutations in their CYT <it>b </it>protein sequences. <it>Plasmodium chabaudi </it>model for studying drug-responses and drug-resistance selection is a very useful rodent malaria model but no ATQ resistant parasites have been reported so far. The aim of this study was to determine the ATQ sensitivity of the <it>P. chabaudi </it>clones, to select a resistant parasite line and to perform genotypic characterization of the <it>cytb </it>gene of these clones.</p> <p>Methods</p> <p>To select for ATQ resistance, <it>Plasmodium. chabaudi chabaudi </it>clones were exposed to gradually increasing concentrations of ATQ during several consecutive passages in mice. <it>Plasmodium chabaudi cytb </it>gene was amplified and sequenced.</p> <p>Results</p> <p>ATQ resistance was selected from the clone AS-3CQ. In order to confirm whether an heritable genetic mutation underlies the response of AS-ATQ to ATQ, the stability of the drug resistance phenotype in this clone was evaluated by measuring drug responses after (i) multiple blood passages in the absence of the drug, (ii) freeze/thawing of parasites in liquid nitrogen and (iii) transmission through a mosquito host, <it>Anopheles stephensi</it>. ATQ resistance phenotype of the drug-selected parasite clone kept unaltered. Therefore, ATQ resistance in clone AS-ATQ is genetically encoded. The Minimum Curative Dose of AS-ATQ showed a six-fold increase in MCD to ATQ relative to AS-3CQ.</p> <p>Conclusions</p> <p>A mutation was found on the <it>P. chabaudi cytb </it>gene from the AS-ATQ sample a substitution at the residue Tyr268 for an Asn, this mutation is homologous to the one found in <it>P. falciparum </it>isolates resistant to ATQ.</p

[Presence of the double pfmdr1 mutation 86Tyr and 1246 Tyr in clones of a chloroquine-resistant west African isolate of Plasmodium falciparum].

Isolates of Plasmodium falciparum from three areas of West Africa were recovered from cryopreservation and their chloroquine-sensitivity were determined in vitro. Of the 90 samples studied, 60 were from Guinea-Bissau (30Resistant/30Sensitive), 15 were from S. Tomé and Príncipe (11Resistant/4Sensitive) and 15 were from Angola (11Resistant/4Sensitive). All the isolates were sensitive to mefloquine. Using the polymerase chain reaction/restriction fragment length polymorphism technique (PCR/RFLP) it was possible to detect two mutations in the pfmdr1 gene, often associated with chloroquine-resistance. 66% of the samples from Guiné-Bissau showed a correlation with chloroquine-resistance while 73% of the samples from São Tomé and Angola altogether had the 86Tyr mutation. The present study on West African isolates and clones showed, for the first time, the presence of a double point mutation in the pfmdr1 gene one being found, up to now, only in South America isolates of Plasmodium falciparum

Concentração de chumbo, defeitos de esmalte e cárie em dentes decíduos Lead level, enamel defects and dental caries in deciduous teeth

OBJETIVO: Verificar a relação da concentração de chumbo no esmalte de dentes decíduos com a presença de defeitos de esmalte e sua relação com cárie dental em pré-escolares. MÉTODOS: A amostra foi de 329 crianças de pré-escolas municipais de uma área próxima de indústrias (N=132) e outra não industrial (N=197) da cidade de Piracicaba, Estado de São Paulo. Essa amostra pertencente a um estudo inicial realizado entre 2000 e 2001 no qual o chumbo foi analisado por meio de biópsia de esmalte. Foram realizados exames clínicos bucais para verificação da prevalência de defeitos de esmalte (Developmental Defects of Enamel Index - DDE, da Federação Dentária Internacional - FDI) e cárie (Índice ceos, Organização Mundial da Saúde), em ambas regiões. Foram utilizados teste de qui-quadrado e cálculo do risco relativo ao nível de significância de 5%, considerando cada região separadamente. RESULTADOS: Houve maior proporção de crianças com cárie entre aquelas com maiores concentrações de chumbo nos decíduos na região não industrial (p=0,02), o que não se observou na região industrial (p=0,89). Houve risco relativo (RR) aumentado de cárie nas crianças da região não industrial o que não foi verificado nas crianças da região industrial. Não se observou relação entre a presença de chumbo e os defeitos de esmalte. CONCLUSÕES: Não foram encontados dados que evidenciassem a relação entre concentração de chumbo e defeitos no esmalte em nenhuma das regiões pesquisadas. Não foi encontrada relação entre chumbo e cárie na região industrial, ressaltando a necessidade de mais estudos dessas relações.<br>OBJECTIVE: To verify the relationship between lead concentration in the enamel of deciduous teeth and the presence of enamel defects and, consequently, with dental caries among preschool children. METHODS: The sample consisted of 329 preschool children in Piracicaba, State of São Paulo: 132 attending municipal kindergartens close to industrial plants and 197 attending kindergartens in non-industrial areas. This sample belonged to an initial study made between 2000 and 2001, in which the lead concentration was obtained by means of enamel biopsy. Oral clinical examination of the children from both regions was performed to verify the prevalence of enamel defects, using the Developmental Defects of Enamel (DDE) Index of the World Dental Federation (FDI), and of dental caries, using the decayed, missing and filled surfaces (dmfs) index of the World Health Organization. The chi-squared test and relative risk calculation were utilized in relation to a significance level of 5%, considering each region separately. RESULTS: Among the children from the non-industrial area, there was a higher proportion with dental caries among those with higher lead concentrations in deciduous teeth (p=0.02). This was not, however, observed among the children from the industrial area (p=0.89). There was an increased relative risk (RR) of caries among the children from the non-industrial area, but this was not seen among the children from the industrial area. No relationship was observed between the presence of lead and enamel defects. CONCLUSIONS: No data was found that would give evidence of a relationship between lead concentration and enamel defects in either of the areas studied. No relationship was found between lead and dental caries in the industrial area, thus emphasizing that more studies of such relationships are needed

Broncoespasmo induzido pelo exercício em adolescentes asmáticos obesos e não-obesos Exercise-induced bronchospasm in obese and non-obese asthmatic adolescents

OBJETIVO: Avaliar e comparar a frequência e intensidade do broncoespasmo induzido pelo exercício (BIE) em adolescentes asmáticos obesos e não-obesos. MÉTODOS: Estudo transversal e descritivo realizado com 39 adolescentes de ambos os sexos, com idade entre dez e 16 anos, divididos em dois grupos conforme o histórico clínico de asma e/ou rinite alérgica e o índice de massa corporal: asmáticos obesos (n=18); asmáticos não-obesos (n=21). Utilizou-se o teste de broncoprovocação com exercício para a avaliação do BIE, considerando-se positiva uma diminuição do volume expiratório forçado no primeiro segundo (VEF1) >15% do valor pré-exercício. Para avaliar a intensidade e a recuperação do BIE, foram calculadas a queda percentual máxima do VEF1 (QM%VEF1) e a área acima da curva (AAC0-30). A análise estatística utilizou o teste exato de Fischer para comparar a frequência de BIE e o teste de Mann-Whitney para a intensidade e recuperação. Rejeitou-se a hipótese de nulidade se p<0,05. RESULTADOS: Não houve diferença significativa na frequência de BIE entre os grupos de asmáticos obesos (50%) e não-obesos (38%). Entretanto, a queda máxima do VEF1 e a AAC0-30 foram maiores nos asmáticos obesos em comparação aos não-obesos (respectivamente 37,7% e 455 versus 24,5% e 214, p<0,03). CONCLUSÕES: A obesidade não contribuiu para o aumento da frequência do BIE em asmáticos e não-asmáticos, entretanto, a obesidade contribuiu para o aumento da intensidade e do tempo de recuperação da crise de BIE em asmáticos<br>OBJECTIVE: To assess and compare the frequency and severity of exercise-induced bronchospasm (EIB) in obese and non-obese asthmatic adolescents. METHODS: Cross-sectional and descriptive study with 39 subjects aged ten to 16 years of both genders divided into two groups according to clinical history of asthma and/or allergic rhinitis and body mass index, as follows: asthmatic obese (n=18) and asthmatic non-obese (n=21). An exercise bronchoprovocation test was applied to diagnose EIB and was considered positive if the forced expiratory volume in one second (FEV1) decreased >15% in relation to pre-exercise FEV1. Maximum percent of fall in FEV1 (MF%FEV1) and the area above the curve (AAC0-30) were calculated to evaluate the intensity and recovery of EIB. Fisher exact test was used to compare the frequency of EIB and Mann-Whitney test to compare the severity and recovery of EIB. Null hypothesis was rejected when p<0.05. RESULTS: No significant difference was found in the frequency of EIB between the asthmatic obese (50%) and non-obese (38%) adolescents. However, the MF%FEV1 and AAC0-30 were significantly higher in the asthmatic obese as compared to the asthmatic non-obese patients (respectively, 37.7% and 455 versus 24.5% e 214, p<0.03). CONCLUSIONS: Obesity did not contribute to the increase of the frequency of EIB in asthmatic and non-asthmatic patients. However, obesity contributed to the increase of severity and recovery time of EIB in asthmatic